Zoonotic Disease - things you can catch from your pet - or not

Dr. Michael Richards

Michael Richards, D.V.M. co-owns a small animal general veterinary practice in rural tidewater Virginia. Dr. Richards graduated from Iowa State University's College of Veterinary Medicine in 1979, and has been in private practice ever since. Dr. Richards has been the director of the PetCare Forum...

Michael Richards, D.V.M. co-owns a small animal general veterinary practice in rural tidewater Virginia. Dr. Richards graduated from Iowa State University's College of Veterinary Medicine in 1979, and has been in private practice ever since. Dr. Richards has been the director of the PetCare Forum...

Ticks

Tickscarry a number of diseases, some of which do have zoonotic
potential (can be transmitted to people). It is best to use one of the
products that kills the ticks continuously without much intervention on
your part. The risk is not high but there is some risk for tick borne diseases
such as Lyme disease, ehrlichiosis and Rocky Mountain spotted fever
when ticks are brought into the household by a family pet.
Ticks may be removed using one of the tick-pulling products or a
forceps (tweezer). It is best not to touch the tick if possible due to
the possibility of tick-borne diseases. If contact does occur, wash
your hands thoroughly. There is a lot of fear of leaving part of the them embedded in the dog when removing ticks but this rarely causes
problems.
There are a number of ways to deal with ticks. The easiest solution is
to use one of the tick killing products that keep them off and/or kill
them if they attach. There are three very effective products that we
use, fipronil (Frontline or Frontline Topspot, Rx), permethrin
(ProTICall, Rx) and amitraz (Preventic collars, Rx).
Frontline kills fleas and ticks effectively. Tick control lasts for 2
weeks to a month. The product should only be applied on a monthly basis
but can be used in conjunction with other products for tick control if
necessary. It works very well for flea control, so if that is also a
problem it may be a good first choice.
ProTICall is a concentrated permethrin topical for tick and flea
control. It is a very effective tick control product but a less
effective for flea control. It lasts 2 to 3 weeks but may be applied at
2 week intervals so it is possible to keep the problem under control
continuously using this product.
Preventic collars are also pretty effective. They have the drawback of
being toxic if ingested. This sounds like it wouldn't be a problem but
dogs will eat these collars right off of another dog, for some reason.
So we don't recommend them for multi-dog households, especially if one
of the dogs is prone to playing with the other dog's collar or if one
of the dogs chews things up frequently. They seem to last around 6 to 8
weeks in our practice area.
Mike Richards, DVM

Heartworm- Zoonotic?

Q: Dr. Richards,
Please help me, I opened a can of worms and I don't know where to go right off to answer to my outburst.
I volunteer for a rescue group here in Orlando, Florida. At lunch today, when four of us were gathered together, someone made the remark, "I wonder if humans can get heartworms?" I blurted out yes without so much as a blink of the eye. I never saw three people come to life so fast. I don't remember where I read it but I read that humans can develop heartworms but I don't know how. Because I could not prove what I said, they don't believe me. I really don't care if I'm wrong, if I am I will apologize but I hope you will be able to clear this up for me. Thank you so much.
Respectfully, Joan
A: Joan
Humans are an aberrant host for heartworms. Basically, what this means is that the microfilaria (baby heartworms) are transferred to humans and they try to follow their normal lifecycle but can't, because they are in the wrong host. This does not prevent them from succeeding in making it partway through their lifecycle, though. So instead of winding up in the heart and pulmonary arteries and living several years, as occurs in dogs, the heartworms usually end up as cysts in the lungs. These cysts look pretty much like lung cancer on an X-ray and a number of humans have had surgery to remove the cyst and/or lung lobes as the result of the resemblance. In addition, on rare occasions, heartworms find another spot in the body with oxygen levels and conditions that support their development and live
there for some time. In humans, a spot that has these conditions is the interior of the eye. So heartworms are occasionally found inside the eye in humans.
I do not know the number of confirmed cases of either of these conditions. However, if you want to make your friends (assuming they might be male) realize the importance of the public health hazard, you could go to the Pub Med web site: http://www.ncbi.nlm.nih.gov/entrez and search on the term "dirofilaria immitis human" and among the first few hits will be an article with this title, "Cas report: Unusual location of Dirofilaria immitis in a 28-year old man necessitates orchiectomy". An orchiectomy is the removal of a testicle.
So keeping your dog and cat on heartworm preventative is not only good for their health, it helps to reduce the incidence of a disease that can have serious impact, although rarely, on humans.
Mike Richards, DVM
2/7/2002

Leptospirosis

Q: Dr. Mike,
Thanks for all the info about canine kidney problems. It has been very helpful. Here's a quick update on Wolf, our 6.5 year old bichon frise who was demonstrating symptoms of kidney failure.
Last night our vet called and told us that Wolf tested positive for leptospirosis. His levels were elevated for 2 of the 5 antibodies they tested for. The vet said specifically Wolf was exposed to grippotyphosa and pomona strains of lepto. Both can cause kidney problems, sometimes permanent, depending on the infection. It seems our vet was wise to get Wolfie on the amoxi immediately as a precaution. He was confident that, with the symptoms and test results, lepto was the cause.
We believe Wolf was eating squirrel poop while we were on walks (at first we thought he was chewing on acorns but then I saw what he was really eating!) and Kay recently recalled that Wolf got to a dead squirrel that was hidden under some leaves. He may have munched on it once or twice before she yanked him away. I suspect either of these could be how he contracted lepto.
We are going to get some more specifics from the vet today but the vet said it would be a good idea to talk to our doctor/pediatrician about the possibility of Wolf passing the lepto to us or Jake (our 9 month old 2-legged furless son). He also recommended testing Glennis, Wolf's sister/littermate. Wolf will finish out his amoxi series (10 days total) and then go on a month of doxicyclin. After the amoxi we'll do some standard bloodwork looking for reduced urea nitrogen and creatinine, globulin level, protein levels, etc.
Eventually we will need to retest Wolfie to confirm he beat the lepto, but the vet wasn't sure if that would be in a month, 6 months or what. He is going to get back to us today on that.
FYI, there is some good info on the net on leptospirosis. I can't remember the site address but using "leptospirosis" as the search word on Yahoo it hit only 3 sites that are all linked. Lots of good info.
Since we are now financial supporters (albeit very minor ones!) of your great website, I might as well ask a couple of quickie questions if you have time:
1) We live in Fairfax, VA, and I see you are just down the road. Do you see or hear much about lepto from other vets in VA? It seems to be relatively rare.
2) Our friend, a microbiologist in a pediatric lab, suggested we confirm with the vet that the elevated antibody levels were NOT caused by his vaccination against lepto which occurred in Mar 98. I would think, however, that the lab would be looking for a significant increase in the antibody level, more than that caused by a vaccination. We'll get the actual numbers today (hopefully), but any thoughts on that since you deal routinely with vet labs and are familiar with their procedures? Could this be a false result due to the
vaccination in March?

3) Will we be able to tell from the lepto tests (antibody levels, type, etc.) how long Wolfie has had the infection? What else can we tell about it? Is he potentially still infected and a carrier? Our vet said to avoid his urine (clean leaks with gloves, etc) and since he licks himself after urinating, his kisses will be off limits until we get to the bottom of this.
4) Ever hear of lepto making the canine-human jump? The vet said it is possible but we should talk to our pediatrician. Our microbiologist friend said that if a human's immune system is down that a zoonosis like lepto might make the jump but she thought it unlikely (but recommended talking to the pediatrician ASAP anyway.)
Well, that's it for now. Thanks for sending us such good info and any more that you have will be appreciated. We'll keep you posted.
S
A: S
To answer your questions:
1) I don't see many cases in which leptospirosis seems likely and have only diagnosed this condition twice in my career. It is possible that I have missed some cases, though. We usually do not consider leptospirosis titers unless there is renal disease in conjunction with other signs, including anemia, low platelet counts, increased white blood cell count and increased liver enzymes or other signs of liver disease or some other reason to suspect it. Since we wouldn't diagnose the condition without at least considering it and testing for it, we may see more cases than we think we do -- or we may not.
2) Veterinary vaccines contain L. interrogans servovars canicola and icterohaemorrhagiae, so titers to L. interrogans pomona and L. interrogans grippotyphosa are not likely to come from the vaccination. Just having a titer to these organisms is not sufficient proof to base a diagnosis on, though. Very high titers (over 1:1000) are considered to be likely to be due to active infection, though. Paired serum titers -- one set taken immediately upon suspicion on the illness and a second set two to four weeks later -- in which there is a rise in the titer, are more likely to be actually due to infection.
3) All you can really tell from the titer is that there has been exposure to the lepto strains, or something that cross reacts with the strains. In the case of high titers it is easier to assume that infection has occurred. It is not possible to tell much else because titers may stay elevated for a long time even after the infection has been eliminated. It is best to assume that Wolf might be a carrier, though. It is just better to be cautious.

4) Infection of humans by pets seems to be unusual but it is possible. Again, it is best to error on the side of caution. An article (Canadian Veterinary Journal, 1991, Prescott et al) says that of 820 cases of leptospirosis in humans from 1962 to 1978 that dogs were implicated as potential sources of infection in 58% of the cases.
Mike Richards, DVM

Sporotrichosis

Q: Sir, Please I need any information you can give me on this disease. I have a male Doberman, that I'm told has been infected. I thought his condition was brought on by a bite from a large horse fly. But after reading about Sporotrichosis I have my doubts. He has developed welts all over his body, especially around his anus. He was put on benadine but became sick to his stomach. I'm afraid he will become dehydrated. He has not been where he could have been punctured by thorns or hay.
A: Dear D-
Sporotrichosis is a fungal disease. It is thought to be spread through contact with infected thorns and from exposure to infected bark (wood) or moss. There has been at least one reported case associated with a bite wound from an alligator.
We have had confirmed cases of this disease in two dogs that I can remember. Both of them had a few nodules on their skin (between 5 and 10) and the nodules drained fluid at times. I am not absolutely certain but I think that both of these dogs had lesions mostly around one front leg and one of them was a doberman, for whatever that is worth. This disease can be hard to positively diagnose in a dog because the fungus can be hard to find on a biopsy. A positive culture from one of the nodules can sometimes be obtained, though.
At present I think that the preferred treatment is itraconazole, one of the newer anti-fungal medications. It is more expensive than sodium iodide but it is reported to be more effective, too.
Nodules and wheals can occur with several skin conditions. If the condition is persisting it would be a good idea to try to get a fungal culture or a skin biopsy in an effort to confirm this condition. If it is easy to visit a veterinary dermatologist that might be a good idea, too. We have seen recurrent wheals (hives) in a couple of dobermans and several dalmatians without being able to diagnose a specific cause. Fortunately they all got better eventually in spite of my inability to diagnose the cause of their problems.
This is potentially a zoonotic disease (can be acquired from the pet by humans). Infection is more common from cats than from dogs but it is a good idea to take appropriate precautions to prevent infection from touching the sores or drainage from the sores.
Mike Richards, DVM

Toxoplasmosis - Dog

Q: My dog has been diagnosed with toxoplasmosis. It started with him shaking and then he started having seizures and was placed on phenobarbitol. Then he started having jaw problems and couldn't keep his jaw closed and consequently couldn't drink water. He did manage to eat dry dog food but with difficulty. The vet said his trigeminal nerve was involved and this also controlled his eyes. His eyes were rolling upwards and he had a hard time focusing or seeing. He was initially placed on Baytril antibiotic and Prednisone and now that they know that it's toxoplasmosis he is on Clindamycin, He also had a tube placed in his stomache so that we could give him water through the tube. He's been on the new antibiotic several days now and seems to be improving. Also I forgot to mention that it has affected his salivary glands and when he tries to drink water, he ends up filling the bowl with saliva.
So my question is, how unusual is this and what is the prognosis?
A: e
Toxoplasmosis and neosporosis, from Toxoplasma gondii and Neospora caninum, respectively, are protozoal infections. They are difficult to tell apart using testing procedures for toxoplasmosis but they are both treated with the same medications so from a practical standpoint it probably doesn't matter which one is actually present. Both diseases can occur in any age dog but tend to occur more frequently in young dogs, less than a year of age.
Infection with toxoplasmosis is probably pretty common. Clinically apparent disease from infection with toxoplasmosis is less common. Dogs can develop central nervous system signs, such as you are seeing, more general signs of illness such as vomiting, diarrhea and fever, respiratory signs such as coughing and heart muscle weakness as a result of infection with toxoplasmosis. Neospora caninum infections cause similar signs. Eye damage can occur with both diseases.
Clindamycin (Antirobe or Cleocin Rx) and trimethoprim/sulfa combinations (Tribrissen, Ditrim, Bactrim, Rx) are the two most commonly prescribed antibiotics for these problems. Control of seizures or other associated problems may also be necessary. Unfortunately, the antibiotics are not capable of eliminating these infections entirely, so recurrences of clinical signs is pretty common and may be induced by anything that suppresses the immune system, such as the use of corticosteroids, other systemic illness, cancer, etc.
I hope that this helps some. I have no idea how frequently problems with salivation or swallowing occur but these can be the result of neurologic disease.
Mike Richards, DVM

Toxoplasmosis -Cats and Human Pregnancy

Q: We recently moved from an apartment to a house with a backyard. My two cats (two year old male and one year old female - both 'fixed') made the transition ok (the female was scared for awhile, but the male seemed excited/happy). Now that it's getting sunny, we've been letting them explore the backyard a bit, but don't want them to stay outdoors (I am pregnant, and would feel safer keeping them away from other cats and 'diseases' until after the baby is born). do you have any suggestions on the indoor/outdoor situation? (ie. should we keep them inside only until the baby's born?) Thank you for all the help, RL
A: The most serious problem during pregnancy that involves cats is an infection with toxoplasmosis during pregnancy acquired by contact with the stool from an infected cat. The risk to the baby increases the later in the pregnancy the new infection is acquired. Since cats are normally infected when they hunt and catch small rodents, it is less likely that one would be infected if it is an inside cat. In addition, the most common site for humans to come into contact with the cat's stools outside is probably in the garden -- cats like to bury their bowel movements in the soft soil in the garden. So keeping the cats in reduces the chance of accidentally coming in contact with cat feces. So I vote for keeping the cats indoors and having your husband do the litterpan cleaning until after the baby is born. Wear gloves while gardening. Be very careful not to eat undercooked meat (a more common route for infection) and wear gloves or carefully wash your hands after handling raw meat.
Mike Richards, DVM

Earmites and People

Q: Hi! I have 4 cats who all have earmites to some degree. The ear drop treatment prescribed by the vet has not been successfull. I am very "close" with my cats and rub heads with them occasionally.. two months ago I noticed a constant noise in my right ear, sounding like a piece of paper being folded, but softer. Now the noise has stopped, but my ear feels congested somehow.. my question is: Can earmites infect human ears? Sincerely, I.
A: There have been reports of earmite infestation in people. This seems to occur only after very close contact with a heavily infested cat. The signs are reported to be intense itching and a soft sound similar to paper being scrunched up in the affected ear. The infection should clear up without treatment in a few weeks if it is present but it would be best to seek medical attention if you think that this is a possible problem.
In multiple cat households it is more effective (at least in our practice) to treat with ivermectin than mitocidal ear drops. Ear mites can live on cat's bodies and they will often survive ear mite treatment due to this unless they are treated there too --- with flea killing products. Plus, in multi-cat households it just seems like the ability to move from cat to cat seems to make the infection a lot harder to control.
Mike Richards, DVM

Hepatitis B or C

Q: Mike is it possible for the family pet to contract Hepatitis C or B from an infectious member of the family (human) after contact with their bodily fluids or excrement. thanks
A: I checked two textbooks that I think are good references and there is no mention of any possibility of contagiousness of Hepatitis C or B from humans to dogs. I also checked an online database -- and was reminded that monkeys can harbor hepatitis B-- but no mention of dogs. I can't say for certain it doesn't occur based on this but it seems pretty unlikely.
Mike Richards, DVM

Everyone Had Diarrhea - Any Common Cause?

Q: Dr Mike, Here is an interesting situation for you........ Two nights ago, my partner and I were suddenly sick with very bad stomach cramps, followed by excessive diarrhea. We attributed it to the lamb stew I had fixed for dinner. However, there were no stomach complaints or vomiting - so food poisoning seemed unlikely. We were feeling completely better after 24 hours. In the middle of that night, my dog got off of her leash in the living room and went to the back off the house, where she defecated twice. She has never done this before. Granted, she is only 6-7 months old, but she has been okay staying inside all night for the last month, so I figured maybe she was sick. Please note - she did not have any stew - nor could she have gotten to it secretly. However - the plot thickens. This morning, we woke up to find that one of our cats had gone to the bathroom all over the floor and litter box in OUR bathroom - also with excessive diarrhea. The cats also would not have had any access to the stew. This seems to me to be too much of a coincidence. I have ruled out any kind of a poison - as I don't keep any around the house at all. Now my question is this. Is there any kind of illness that can affect canines, felines AND humans??? Also, it may be important to mention that we are located in Sydney, Australia - so we are cut off from many diseases like rabies and such. I am hoping that you may be able to shed some light on this situation. I am not terribly worried - more an acute case of curiosity!! Best regards
A: I am not aware of any diseases offhand, other than the food poisonings like staph and E. coli and the intestinal parasite giardia that would commonly affect all three species. There is some debate over whether or not giardia is species specific (there may be subspecies only able to infect a limited number of host species). It is commonly associated with contaminated water supplies.
I guess that isn't much help but you might consider calling your public health department (or whatever it is called in Australia) to ask this, too. You may have a problem that isn't common here in America.
Mike Richards, DVM

Zoonotic Aspects of Giardia in Dogs

Q: If a person has had contact with a giardia-infected dog but was unaware of the bacteria's presence and didn't practice good sanitation, what can be done? Please respond, someone very close to me has infected dogs and many people have played with them unwittingly (though none have shown signs of it, based on the symptoms I was taught in Boundary Waters MN), and we do not want to be infected. What are the signs in people, and can you refer me to good informative sites about this?
Thank you,
E
A: E
There is still controversy over whether or not giardiasis is a zoonotic disease -- a disease that can be passed from pets to humans. According to Drs. Leib and Zajac, writing in Kirk's Current Therapy XII, the dog and human strains of giardia have different characteristics while the cat and human strains are more similar. However, until there is definite proof one way or the other it is a good idea to consider contact with fecal material from infected dogs to be potentially infective to humans.
As you point out, good sanitation, such as hand washing after playing with the dogs and avoiding contact with the dog's feces is the best defense against this condition. Giardia species are water-borne protozoans and contaminated water sources are probably the most likely source of infection for both pets and people.
Metronidazole and fenbendazole are reasonably effective at eliminating Giardia organisms from infected pets so treatment of the dogs would be a good idea. Metronidazole is inexpensive so financial concerns shouldn't prohibit treatment in most cases.
I am not sure if people have the same signs as dogs but the giardiasis in dogs is often asymptomatic (i.e. the dogs are not sick at all) but it may cause diarrhea.
You can probably find a lot of information on giardia at the PubMed site. We have a link to it from our link page.

Mike Richards, DVM

Giardia - Cats

Q: Dear Dr. Mike: I have three Maine Coon cats, one of which was diagnosed with giardia several months ago by our veterinarian. His only symptom was foul smelling diarrhea. He was originally treated with furazolidone for 10 days, which stopped the symptoms. Approximately 1 month later, the symptoms started again. At this time, all three cats were treated with furazolidone. The symptoms reoccurred sometime after the treatment was completed. Then all three were treated for ten days with metronidazole. We also began changing and disinfecting the litter boxes twice per day. Then the same scenario; a reoccurance of the symptoms in the same cat. All three are currently on another 10 day treatment regimen of metronidazole. Our veterinarian plans another 10 day treatment for the cat with the recurring diarrhea.
My questions are: 1. Is this the most effective treatment for giardia? 2. Where could my cats come in contact with this? (They are inside cats, their only contact with the outside world is when they go to the groomer, which I discontinued after the first round of treatment.) The youngest, who has the recurring symptoms, was bought from a reputable breeder in February 1995. Could he have had the parasite without symptoms since then? 3. Is it possible for giardia to be transmitted to my family? 4. How long does it usually take to eradicate this parasite? We are becoming frustrated by the constant pilling and litter box disinfecting. This has gone on for months. My loving cats now avoid me for fear that I may open their mouth and push an unpalatable pill down their throat. Thank you for any advice that you can give. A.
A: A- There are five medications that I know of that can be used to treat giardia. Quinacrine, which is not available in the United States, is used in dogs for giardiasis but may not be effective in cats. Furozolidone (Furox Rx), metronidazole (Flagyl Rx), albendazole (Valbazen Rx) and fenbendazole (Panacur Rx) have all been recommended for use against Giardia in dogs and cats. There are many more reports of resistance to medication for giardiasis in cats than in dogs, so it may not be that unusual to have such a hard time treating the problem, although we seem to have been lucky and have not had a case similar to yours for resistance.
We have not used furazolidone and have no personal experience with success rates using it. We have not used albendazole, either. We usually start treatment with metronidazole at 50mg/kg/day for 5 days. Most of the time that has worked well for us but we have seen a few resistant cases. We have used fenbendazole at 50mg/kg/day for 5 days to treat these cases and it has worked effectively for us in this situation so far. We have tried using fenbendazole first and have had one case where it didn't work as the initial agent but metronidazole helped. I am not sure that there is a "best" medication for giardia. I think that it just seems necessary to start with one of the recommended medications and use others if that one doesn't work.
Giardia have a cystic stage which is excreted in the feces. The cysts can live for several months if they are not exposed to sunlight or dried out. Quaternary ammonium disinfectants (like Roccal Rx) may be the best disinfectants but live steam cleaning of infected catteries has been suggested and I am sure I have seen at least one reference which suggested that chlorine bleach diluted 1:30 was reasonably effective, as well. Obviously most people are not going to be able to steam clean their house. Giardia have a direct infective cycle (no intermediate host). The cysts are picked up orally from contaminated surfaces or water. We have had one client who reported that giardia was found in their well water.
It does seem a little odd that your inside only cats are affected with this parasite but due to the problems with resistance any one of your cats may have been a carrier of the organism. Immune incompetency (cats infected with feline leukemia or feline immunodeficiency virus or stressed severely in some manner) may contribute to resistance or ease of infection. It may be a good idea to check for these diseases.
I think I'd also consider the possibility that something else is going on unless giardia have been isolated from the stool again after the treatments.
I don't think anyone knows for sure whether or not giardia can be transferred from pets to humans. There is some variation among strains of giardia and this may mean that there is a lower probability of infection between species than some people think. On the other hand, it makes it possible for the traits of the strains to overlap enough that perhaps infection between species is possible. I'd be cautious and wash hands after handling the cats, cat toys, litterpans and food bowls. Clean the house as well as you can, disinfecting surfaces for which that is possible with quaternary ammonium (preferably) or chlorine bleach disinfectants.
Mike Richards, DVM

Rash after Cat Licked Hand

Q: Dear Dr. Mike: After looking through the questions about cats and not finding an area dedicated to problems that owners can develop from their pets I thought I would ask you my questions. We have recently adopted a stray cat (approx. 6 mos old). She spends most of the day outside. I have been playing with her letting her lick my hands and face. I have now developed a rash across the knuckles of one hand that looks like poison ivy rash. The rash is itchy, raised and slightly red. Any ideas if this could have been caused by the cat licking my hand. Just last week she went to the local Vet's for her vaccines, etc. and seems to be in good health. (I was especially careful to not let her claw this hand as I have had lymph nodes removed on this side and have been cautioned to be wary of infection in this hand and arm.) Any insight you can give me would be appreciated...
A: I can think of a couple of problems that might cause the symptoms you are seeing. Pets do sometimes transfer poison ivy toxins from the environment to their owner's, so a poison ivy reaction is entirely possible. There are some people with allergies to cats who develop rashes on contact with them -- but I think they are usually more generalized. Ringworm (dermatophytosis), a fungal disease that many people are susceptible to can be transferred from a cat to its owner. This is probably the most common skin disease in human owners from association with cats. Many cats are carriers of this condition and show no outward signs.
It would be best to consult with your dermatologist if the rash persists. He or she will be able to tell you if there is a liklihood of a zoonotic (caught from an animal) disease. If this is ringworm, your vet can treat your cat so that does not reinfect you.
Hope all is well at this point.
Mike Richards, DVM

Pet Feces and Children

Q: My grand mother told me that dog feces can be very poisoning to a child if it is swallowed, or comes in contact with their eyes. I was wondering if this is true? thanks
A: There are no poisons in dog's feces, unless the dog ingested a toxin prior to having the bowel movement. There are good reasons to discourage children from handling dog or cat feces, though -- and to teach them to wash their hands carefully when contact may have occurred. Dogs sometimes have intestinal worms which can cause problems if the eggs or infective larvae are transmitted to people. The effects can include local irritation at the site of infection in the case of hookworms or damage to the eyes or cysts in the lungs if the case of roundworms. These are rare problems but they do occur and it is wise to avoid contact with dog stools due to this.
Cats may also transmit Toxoplasmosis through their stools. This can cause serious problems if a woman is infected during pregnancy and can lead to neurologic disease or eye damage in humans. Toxoplasmosis is more commonly acquired from eating undercooked infected meat but there is no reason to take any risk - avoid contacting cat feces directly and wash your hands (or the children's hands) thoroughly if contact occurs. So your grandmother was right in one way, contact with dog stools or cat stools can eventually lead to eye problems, but not through a toxic reaction.
Mike Richards, DVM

Michael Richards, D.V.M. co-owns a small animal general veterinary practice in rural tidewater Virginia. Dr. Richards graduated from Iowa State University's College of Veterinary Medicine in 1979, and has been in private practice ever since. Dr. Richards has been the director of the PetCare Forum...